Furnace wall



1945. R. SHELLENBERGER ET AL 2,368,265

FURNACE WALL Filed July 27, 1940 Plasiic fnsu/aiz'or;

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Patented Jan. 30, 1945 UNITED STATES PATENT ornca FURNACE WALL Rolfe Shellenberger, Westfield, and Frank X. Gilg, Cranford, N. J., asslgnors to The Babcock & Wilcox Company, Newark, N. J., a corporation of New Jersey 4 Claims.

This invention relates to heat exchange apparatus and it is more particularly concerned with the improvements in a furnace wall or in a gastight setting confining a gaseous heating medium for fluid heat exchange apparatus such as steam generators.

An object of the invention is to provide a gastight boiler setting wall or furnace wall which will substantially prevent the leakage of gas through the wall. It is also an object of the invention to accomplish this result without expensive metallic casings about the setting wall.

More specifically, the inventioninvolves a boiler setting wall which includes a sealing medium disposed between two other-wall strata. One of the latter, between the high temperature heating gases and the sealing medium, prevents the latter from reaching such a high temperature that it will become too fluid to maintain its sealing effect. The other wall stratum is disposed externally of the sealing stratum, its function being to prevent the sealing material from being so changed by exposure to the atmosphere or lower temperature medium that it will become hardened or otherwise lose it plasticity or sealing effect.

The invention will be described with reference to the accompanying drawing, and other objects of the invention will appear as the description proceeds.

In the drawing:

Fig. 1 is a section through a boiler setting wall consisting of firebrick, an insulating stratum, and a plastic sealing stratum covering the insulation;

Fig. 2 is a section through a boiler settin wall which includes wall cooling tubes connected into the boiler circulation, the spaces between these tubes being closed by Wall blocks and a sealing stratum being disposed exteriorly-of the tubes between two strata of insulation; and

Fig. 3 is a section of a boiler setting wall which includes wall cooling tubes with the spaces between these tubes being closed by refractory material maintained by metallic studs secured to the tubes and extending into those spaces. Externally of the tubes a plastic sealing compound is disposed as a stratum between two thermal insulation strata.

The boiler setting walls are exposed on their interior surfaces to a heating medium at high temperature, and the inner structures of such walls must therefore have considerable heat resistance. When heat resistant firebrick are employed for these parts of the walls, there is apt to be gas leakage through the brick, and between them. A thermal insulating stratum exteriorly of such refractory material is also subject to gas volves a sealing stratum I0 covering the exterior surface of the insulation stratum l2 and maintained in such condition that it retains its sealing effect under operating conditions.

The sealing stratum I0 may consist of a bituminous material with asbestos or other heat resisting material incorporated therewith and the insulating effect of the stratum I2 is so co-ordinated with the similar effect of the firebrick l4 that the material of the sealing stratum l0.is pre vented from becoming so fluid that it 'will not maintain its upright position covering substantially the entire face of the stratum l2. The sealing stratum might also be of sheet material involving a medium which would become plastic or have a sealing effect upon the application of heat and/or pressure.

Externally of the sealing stratum I0 is a finishing stratum l6 which may be installed as a plastic or in block form. It preferably has such a protective or insulating effect that it prevents the material of the sealing stratum ill from losing its sealing effect by becoming hardened or otherwise attaining a non-plastic condition.

The type of furnace wall indicated in Fig. 2 of the drawing is adapted to be employed in the first open pass of a steam generating installation such as that shown by Patent #2,196,889, E. G. Bailey et al., April 9, 1940. It involves wall cooling tubes Iii-20 connected into the fluid system of the generator and spaced apart. The furnace face of the Fig. 2 wall is formed by wall tile or cast iron blocks such as those shown at 22 and 24. They close the spaces between the tubes and are so held in position on the tubes that they maintain the latter in their spaced relationship. These tiles are shown secured in good heat exchange relationship with the tubes by backing members 26 and 28 which co-operate with the stud bolts 30 and 32 in a manner which will be clear from the disclosure.

Exteriorly of the tubes l8-20 is a primary stratum 34 of thermal insulation. This stratum has a thermal effect similar to that of the stratum 12 of the Fig. 1 wall, to prevent the sealing stratum 36 from reaching such a high temperature that it loses its plasticity or sealing effect.

- The primary insulation stratum 34 may be held in place by the use of a wire mesh 38.

The sealing stratum 3B of this wall may consist of such a bituminous mixture or compound as that above indicated, preferably applied in a plastic condition over the surface of the stratum 34. Thereafter a wire mesh 40 may be disposed exteriorly of the stratum 36 and then a finishing stratum 4| disposed in block or plastic form over the wire mesh and the sealing stratum 36. This finishing layer or stratum 4| is intended to have such a protective or insulating effect upon the plastic material of the sealing stratum 36 that the latter will not become so hardened or otherwise affected that it will lose its plasticity or its sealing effect.

The wall construction indicated in Fig. 3 includes the wall cooling tubes 4244, connected into the fluid system of a boiler and provided with rows of studs 46-49 preferably welded to the tubes and extending into the inter-tube spaces. The spaces between the tubes 42-44 are closed by a refractory material such as plastic chrome ore installed around the studs.

The primary stratum 50 of thermal insulation is disposed between the tube 42- and it is held in place by wire mesh 52. This stratum is of such thickness and of such thermal insulation effect that it prevents the material of the insulating stratum 54 from becoming so fluid that it loses its sealing effect.

Exteriorly of the sealing stratum 54 is an exterior finishing stratum 56 having much the same effect as the exterior stratum of the Fig. 2 wall and maintained in its operative position by wire mesh 58 disposed exteriorly of the sealing stratum 54 before the stratum 56 is applied.

In each of the embodiments shown, there is a thick inner stratum subject to the heat of the gaseous heating medium. When this stratum includes the tubes and the refractory material as indicated in Figs. 2 and 3, it is subject to gas leakage, and when the inner stratum involves firebrick as indicated in Fig. 1, that stratum is still subject to gas leakage. Such leakage would be more pronounced when porous firebrick are utilized, and the leakage would also tend to increase as an induced draft fan, or a stack, is approached.

In each of the modifications shown, there is an insulation stratum next outwardly of the inner stratum, and this insulation stratum is also subject to gas leakage. The outer surface of the insulation stratum, in each embodiment, is covered by a sealing stratum to prevent gas leakage. The inner stratum and the insulation stratum both function to keep the temperature of the outer surface of the insulation stratum below a value at which the sealing compound would run, or would otherwise be caused to lose its sealing effect on the outer surface of the insulation stratum. Also, the sealing stratum is covered by a thicker insulation stratum which protects the sealing compound and prevents it from losing its sealing effect because of atmospheric exposure.

Although the invention has been described with reference to the details of preferred embodiments shown in the drawing, it is to be appreciated that the invention is not necessarily limited to all the details thereof. It is rather to be considered as of a scope commensurate with the scope of the subjoined claims.

What is claimed is:

1. In a casing or furnace wall for steam generators or other fluid heat exchange installations; a wall including heat absorbing wall tubes, refractory material closing the spaces between the tubes, a primary stratum of thermal insulating material exteriorly of said refractory material and producing a substantial part of the total insulating effect of the entire wall, an intermediate stratum of a plastic sealing medium including a bituminous material and constituting a. gastight layer covering the outer surface of the primary stratum, a secondary stratum of low heat conductivity exteriorly of the layer, and metallic re-enforcing material for assisting in maintaining the sealing layer in its operative position, the primary and secondary strata being operative to prevent such changes in the sealing layer that it would lose its plasticity or its sealing effect.

2. In a casing or furnace wall for steam generators or other fluid heat exchange installations; a wall including heat absorbing wall tubes, ref ractory material closing the spaces between the tubes, a primary stratum of thermal insulating material exteriorly of said refractory material and producing a substantial part of the total insulating effect of the entire wall, an intermediate stratum of a plastic sealing medium including bituminous material constituting a gas-tight layer covering the outer surface of the primary stratum, and a secondary stratum of low heat conductiviity exteriorly of the sealing layer, the primary and secondary strata being operative to prevent changes that might cause the sealing layer to lose its plasticity or its sealing effect.

3. In fluid heat exchange apparatus in which a high temperature gaseous heating medium is utilized under sub-atmospheric pressure; a 0215' ing or wall construction confining the heating medium and including a pervious refractory inner stratum subject on its inner surface to the heat of said medium; a pervious second stratum of heat insulating material next outwardly of the inner stratum; a sealing stratum covering the outer surface of the second stratum; the sealing stratum being of such properties that its plasticity may be so increased by a temperatur rise that it acts as a liquid; said second stratum normally acting to maintain the temperature of the sealing stratum below a value at which its sealing effect would be impaired by the heat of said medium; and an outer stratum of low heat conductivity covering the sealing stratum and preventing atmospheric exposure of the latter; the sealing stratum being much thinner than said inner stratum.

4. In a furnace or heating structure for fluid heat exchange apparatus or the like in which a high temperature gaseous heating medium is utilized under sub-atmospheric pressure; a casing or wall construction confining the heating medium and including a combined pervious ceramic refractory and heat resistant inner section subject on its inner surface to the heat of said medium; a sealing stratum including bituminous material and covering the outer surface of the inner section; the sealing stratum being of such properties that its plasticity may be so increased by a temperature rise that it acts as a liquid; said inner ection also having thermal insulation characteristics effective to prevent excessive heat transfer from the heating medium to the sealing stratum and to thereby maintain the temperature of the sealing stratum below a value at which it loses its plasticity or sealing effect; and an outer stratum of low heat conductivity covering the sealing stratum and preventing atmospheric exposure of the latter; the sealing stratum being much thinner than the inner section.

ROLFE SHELLENBERGER. FRANK X. GILG. 

